Huge lobster-like animal filtered seawater for food 480 million years ago, say fossil hunters

By Ben Miller | 18 March 2015

Zoologists say oldest example of gigantism, named after Moroccan finder, "fills ecological hole"

A photo of a reconstruction of a large lobster-like creature in a deep turquoise sea
A reconstruction of how the newly-discovered anomalocaridid might have looked feeding on a plankton cloud in the sea around 480 million years ago© Reconstruction by Marianne Collins, ArtofFact
A two-metre long lobster-like animal that lived 480 million years ago used spine-covered 'limbs' on its head to sift seawater and trap tiny particles of food, according to experts investigating fossils believed to represent the earliest giant filter-feeder ever discovered.

Named Aegirocassis benmoulae, after Mohamed Ben Moula, the Moroccan fossil hunter who discovered the remains, the huge sea dweller had paired swimming flaps along its body.

Dr Peter Van Roy, of Yale University, used tiny needle-like tools to chip away at the rock surrounding the discovery, revealing an “exceptionally well-preserved” 3D fossil of the species.

“This would have been one of the largest animals alive at the time,” says Dr Allison Daley, a colleague of Dr Van Roy’s on the study who works at Oxford University’s Department of Zoology.

A photo of a large dark brown and grey fossil specimen from prehistory
The complete specimen of the aegirocassis benmoulae© Reconstruction by Marianne Collins, ArtofFact
“These animals are filling an ecological role that hadn’t previously been filled by any other animal.

“While filter feeding - filtering water to find food - is probably one of the oldest ways for animals to find food, previous filter feeders were smaller and usually attached to the sea-floor.

“We have found the oldest example of gigantism in a freely swimming filter feeder.

“Without these 3D remains, we may never have got the insight into these animals’ anatomy that we did.”

Part of an extinct marine animal family called the anomalocaridids which first appeared 520 million years ago, the animal’s flaps are likely to have been precursors to the “double-branched” legs which anthropods such as spiders and insects use to notably versatile effect, including sensing the environment, feeding and mating.

Although most anomalocaridids were sharp-like apex predators, possessing spine-covered head limbs and a circular ring of sharp teeth for a mouth, the new species is closer to a whale.

  • The full report has been published in the journal Nature.

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An image of a reconstruction of a large turquoise image of a whale-like creature against black
Aegirocassis reached a length in excess of two meters, making it one of the biggest arthropods to have ever lived. It foreshadows the later appearance of giant filter-feeding sharks and whales© Reconstruction by Marianne Collins, ArtofFact.
A photo of a female zoologist kneeling down to dig at a bit of light brown coastal rock
Allison Daley at a fossil dig in the Emu Bay Shale in Australia. This area has yielded many previous Anomalocaridid fossils© Photo: J Paterson, UNE
A photo of a female zoologist crouching on pebbles carrying a jagged bit of rock
The zoologist with an Anomalocaridid fossil at the Burgess Shale in Canada© Photo: Parks Canada
A close-up photo of a light brown and yellow fossil showing the bones of a marine creature
A fossil showing the full-length side-view of the spiny 'net' which Aegirocassis benmoulae used to filter its plankton food from sea water© Photo: Peter Van Roy, Yale University
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Science at its best.....using the evidence to fit their theory.
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